This invention pertains to skeletal iron catalysts, and particularly pertains to catalyst composition and preparation methods and processes for use of such skeletal iron catalysts in Fischer-Tropsch synthesis processes for CO and H.sub.2 feeds to produce hydrocarbon products.
As a basic technology for producing synthetic liquid fuels from CO+H.sub.2 feedstreams, the Fischer-Tropsch (F-T) catalytic synthesis process has undergone worldwide development and use since the 1920s. Iron-based catalysts have been widely investigated and used, and precipitated iron catalyst and fused iron catalyst have been the commonly used catalysts in such F-T synthesis processes. However, the preparation procedure for the precipitated iron catalyst is undesirably complicated and includes several steps of precipitation, washing, filtration, drying, formation, calcination, pulverization, and reduction. Also, the precipitated iron catalyst is significantly influenced by various parameters, including precipitating agent, solution concentration, precipitation temperature, solution pH value, pretreatment temperature, and atmosphere, and such catalyst is undesirably expensive. Furthermore, the fused iron catalyst has undesirably low active surface area (.about.10 m.sup.2 /g) that is difficult to increase, and it also has low catalytic activity and minimal economic advantage. Both of these two known iron catalysts provide only conventional hydrocarbon product selectivity. On the other hand, since development of the known skeletal nickel catalyst systems, such skeletal type catalysts have been used in organic reactions, particularly in liquid phase hydrogenation systems. Some previous development work has been focused on skeletal nickel catalyst and worked only on some simple hydrogenation reaction systems. Because of the desirability for improving the activity and selectivity of iron catalyst for Fischer-Tropsch synthesis processes, development of an improved skeletal iron catalyst was initiated.